The disclosure of Japanese Patent Application No. 2000-340626 filed on Nov. 8, 2000 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The invention relates to an intake air amount computing apparatus for computing an amount of air drawn into an internal combustion engine and a method for the same, and an intake pressure computing apparatus for computing an intake pressure of an intake pipe connected to the internal combustion engine and a method for the same.
2. Description of the Related Art
An engine control apparatus has been known as an apparatus for computing the amount of air drawn into the internal combustion engine, as disclosed, for example, in Japanese Patent Application Laid-Open HEI 9-158762. The engine control apparatus for computing a first variation per unit time based on a measured intake air amount and a second variation per unit time based on a throttle passing air amount obtained through arithmetic operations and, by comparing the first variation with the second variation, corrects a cylinder inflow air amount. This engine control apparatus aims to eliminate any delay in the control system by correcting the cylinder inflow air amount through the comparison made between the first variation and the second variation.
However, in the above-mentioned apparatus, the cylinder inflow air amount is computed on the assumption that all air flowing into the cylinder passes through the throttle, which could result at times in incorrect computation of the cylinder inflow air amount. If a passage through which air is supplied to the cylinder is constructed so that air drawn in from another passage without passing through the throttle valve joins the main inflow in conjunction, for example, with a purge or EGR, an error is introduced to the cylinder inflow air amount, which causes computation of the inflow air amount to be inaccurate.
In viewing the foregoing technical problems, it is therefore an object of one aspect of the invention to provide an intake air amount computing apparatus with improved accuracy in computing the intake air amount and a method for the same, and an intake pressure computing apparatus with improved accuracy in computing the intake pressure and a method for the same.
Namely, an intake air amount computing apparatus and a method for the same according to a first aspect of the invention compute a first intake pipe pressure based on a sum of, at least, a throttle passing air amount calculated based on a throttle opening and an amount of air that flows into the intake pipe through a passage other than passage through a throttle valve. The intake air amount computing then compute a second intake pipe pressure based on an output from an air flow meter, and compute, based on the first intake pipe pressure and the second intake pipe pressure, an amount of air drawn into an internal combustion engine.
The first intake pipe pressure may also be computed by the first intake pipe pressure computing device based on a sum of the throttle passing air amount and a flow of purge air that flows into the intake pipe through a purge passage.
The first intake pipe pressure may also be computed by the first intake pipe pressure computing device based on a sum of the throttle passing air amount and an amount of exhaust gases that flow into the intake pipe through an exhaust gas recirculation passage, or an exhaust gas inflow amount.
An intake pressure computing apparatus and a method for the same according to a first aspect of the invention compute a first intake pipe pressure based on a sum of, at least, a throttle passing air amount calculated based on a throttle opening and an amount of air that flows into the intake pipe through a passage other than that through a throttle valve. The intake pressure computing apparatus then computes a second intake pipe pressure based on an output from an air flow meter, and compute, based on the first intake pipe pressure and the second intake pipe pressure, a pressure in the intake pipe.
The first intake pipe pressure may also be computed based on the sum of the throttle passing air amount and the flow of purge air that flows into the intake pipe through the purge passage.
The first intake pipe pressure may also be computed based on the sum of the throttle passing air amount and the amount of exhaust gases that flow into the intake pipe through the exhaust gas recirculation passage, or the exhaust gas inflow amount.
According to these aspects, the intake air amount is computed including the air that flows into the internal combustion engine through the purge passage or the like to join the main inflow without passing through the throttle valve. This enables accurate computation of the intake air amount or the intake pipe pressure even with the intake air that flows into the internal combustion engine without passing through the throttle valve.
In addition, in place of the output of the air flow meter with a response delay and the purge flow rate without any response delay being directly added up, a specific intake pipe pressure is computed using the air flow meter output or the purge air flow individually so as to compute the intake air amount and the intake pipe pressure based on each of these intake pipe pressure values. This enables accurate computation of the intake air amount and the intake pipe pressure, without causing an error due to incompatibility between the air flow meter with a response delay and the purge flow rate without any response delay.